This application is based on application No. 2000-176845 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a tandem-type color an image forming apparatus such as a printer and copying machine.
2. Description of the Related Art
So-called tandem type color image forming apparatuses are known which have a plurality of image forming units respectively accommodating toners of different colors arranged in parallel along an intermediate transfer belt, such as that disclosed, for example, in Japanese Laid-Open Patent Application NO. H7-28294.
In this type of image forming apparatus, images of respectively different color are superimposed one upon another on an intermediate transfer belt by the image forming units, and these overlaid images are transferred to a sheet used as a recording medium. Then, when the sheet passes through a fixing unit, the image on the sheet is heated and fixed to the sheet, and subsequently ejected to a discharge tray.
In an image forming apparatus wherein a plurality of image forming units are arranged along an intermediate transfer belt as previously described, each image forming unit and the intermediate transfer belt are removable from the apparatus in the direction of the rotational axis for jam handling and maintenance. However, when removing each image forming unit and the intermediate transfer belt in the rotational axis direction, a large opening must be provided, for example, in the frame on the front side of the apparatus body. For this reason a disadvantage arises inasmuch as the rigidity of the frame of the apparatus body is reduced. Furthermore, the rotational axis of the image forming units and the intermediate transfer belt are supported only by the frame on the interior side. For this reason it is difficult to support the rotating shafts of a plurality of image forming units in parallel, such that the images formed by the image forming units become skewed so as to disrupt the image.
In view of these disadvantages, an object of the present invention is to provide an image forming apparatus capable supporting the rotating shafts of image forming units in parallel without reducing the rigidity of the frame of the apparatus body, so as to form images which are not disrupted.
These objects are attained by the image forming apparatus of the present invention comprises: a belt unit having a frame, and at least three rollers supported by the frame, and an intermediate transfer belt supported on the exterior surface of the three rollers, and wherein the intermediate transfer belt includes a horizontal belt section; a plurality of image forming units arranged opposite the horizontal belt section of the intermediate transfer belt for overlaying images of different colors to form an overlay image; and a transfer device for transferring the overlay image formed on the intermediate transfer belt onto a sheet; wherein the belt unit is supported so as to be removable from the image forming apparatus in a direction perpendicular to the roller shafts and parallel to horizontal belt section.
According to this construction, since the belt unit is removable from the image forming apparatus in a direction perpendicular to the roller shafts and parallel to the horizontal belt section, the opening formed in the frame of the apparatus is smaller than an opening to allow removal parallel to the roller shafts, and rigidity of the frame is not reduced. For this reason the rotating shafts of the image forming units can be supported in parallel each other so as to produce disrupted images.
According to another aspect of the present invention, the image forming apparatus comprises a belt unit having a frame, and at least three rollers supported by the frame, and an intermediate transfer belt supported on the exterior surface of the three rollers, and wherein the intermediate transfer belt includes a horizontal belt section; a plurality of image forming units arranged opposite the horizontal belt section of the intermediate transfer belt for overlaying images of different colors to form an overlay image; a transfer device for transferring the overlay image formed on the intermediate transfer belt onto a sheet; and a body frame for containing the belt unit and the image forming units and having a first vertical frame in which an opening is formed to remove the belt unit in first direction and a second vertical frame in which an opening is formed to remove the image forming units in second direction.